Rates of women who are opting for preventive mastectomies, such as Angeline Jolie, have increased by an estimated 50 percent in recent years, experts say. But many doctors are puzzled because the operation doesn't carry a 100 percent guarantee, it's major surgery -- and women have other options, from a once-a-day pill to careful monitoring.

The danger to students is uncertain, and EPA does not know for sure how many schools could be affected. But the agency is telling schools that they should test old caulk and remove it if PCBs turn up in significant amounts.

EPA Administrator Lisa Jackson said PCBs remain in schools and many other buildings built before the chemicals were banned in the late 1970s.

"We're concerned about the potential risks associated with exposure to these PCBs, and we're recommending practical, common sense steps to reduce this exposure as we improve our understanding of the science," Jackson said in a news release issued Friday.

The agency said it would conduct new research into the link between PCBs in caulk and in the air, which it said is not well understood. The agency also will conduct its own tests on PCBs in schools.

EPA now recommends testing for PCBs in peeling, brittle, cracking or deteriorating caulk in schools and other buildings that were built or renovated between 1950 and 1978. The caulk should be removed if PCBs are found at significant levels, the agency said.

Earlier this month, a Bronx, N.Y., mother sued New York City over PCBs in caulk at her daughter's public school.

PCBs, known formally as polychlorinated biphenyls, are chemicals that were widely used in construction and electrical materials — they made caulk more flexible — before they were banned 30 years ago. PCBs can hurt the immune, reproductive, nervous and endocrine systems and can cause cancer if they build up in the body over long periods of time.

Hundreds of the 80,000 public school buildings across the country were built between 1950 and 1978, though it is difficult to say exactly how many.

A decade-old Education Department report said the average building was 40 years old, and the Rebuild America's Schools coalition says that two-thirds of schools have an environmental problem such as the presence of cancer-causing asbestos or radon gas, lead in water and paint, leaking underground storage tanks or cancer-causing radon gas.

Copyright 2009 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.